Need new PSU? x1800xt

Here's some background on power supplies which (I hope) will help you.

The power supply converts power coming into your computer from the wall
outlet to the forms usable by the electronics in the system. It changes incoming alternating current (AC) at 120 or 240 volts to direct current (DC) at 3.3, ±5 and ±12 V.

A good power supply does more than power conversion — it cleans up the spikes, surges, and sags in the utility power. Motors, copiers, appliances, and other electrical devices create noise in the power at your wall outlet, as do lightning strikes and other effects farther away. If that noise gets through the power supply into the electronics in the computer, it causes trouble ranging from erratic operation to complete shutdown.

A high-quality power supply will be more resistant to these problems, giving you more reliable operation from your computer.

You need to know four electrical terms to understand and compare power
supplies — voltage, current, power, and frequency.

Voltage is the force pushing electricity through the wire. It’s like the
water pressure in your garden hose: More voltage is like more water
pressure. Voltage is measured in volts (abbreviated V). In North
America, common wall-outlet power is at 120 V. European power is
commonly 240 V.

Current is the amount of electricity flowing through the wire and is
like the flow of water through a hose. Current is measured in
amperes (or amps, abbreviated A).

Power is the product of voltage and current (voltage times current),
and is measured in watts (abbreviated W). If your computer draws 3
amps at 120 V, it uses 360 W.

Frequency is the rate at which the power alternates between positive and negative voltages. Frequency is measured in Hertz (abbreviated Hz); a Hertz is one cycle per second. North American power arrives at 60 Hz; European power is mostly 50 Hz.